Staghorn corals of the deep - a cradle of life for threatened coral reefs?

Image: The Deep Reef team sorting through coral samples

Catlin Seaview Survey researchers have documented staghorn corals, including newly recorded species, for the first time in deep waters of the Great Barrier Reef and Coral Sea. Our researchers used remotely operated vehicles (ROVs) and a deep diving team to explore corals in the mesophotic zone (below 30 m in depth), and found staghorn coral colonies growing to depths of around 70 m.

New species of the deep

Staghorn corals (genera Acropora and Isopora) are the most common corals found in most shallow reef systems but were thought to be scarce in deeper water. However, 38 staghorn species were documented in this study, including several very large coral colonies, three species newly recorded for Australia and five species that weren’t found in the shallow waters. The newly recorded species were previously considered rare and endangered due to their limited distribution in central Indonesia and the far western Pacific.

A deep refuge for coral

The mesophotic reef may provide a “deep refuge” for some coral species in the event of severe storms or mass bleaching events, which typically have a more pronounced effect in the shallow reefs. This study found that around a third of Great Barrier Reef and Coral Sea staghorn corals are shared between the shallow and deep reef, and may therefore find refuge in the deep. These deep populations have the potential to contribute to shallow-reef recovery by providing a reproductive source for the shallow-reef areas.

Staghorn corals have long been regarded as typical shallow-water corals, but this work demonstrates the significance of these corals in the mesophotic reef and the importance of considering this zone in future reef management strategies.